Process for reclaiming film scrap with an alcoholic alkali solution



Patented Aug. 8, 1933 Ul llTED STATES PATENT OFFlCE PROCESS FOR RECLAIMING FILM SCRAP WITH AN ALCOHOLIC ALKALI SOLUTION tion of New York No Drawing.

Application May 24, 1930 Serial No. 455,452

13 Claims.

This invention relates to the reclamation of dyed photographic film scrap having a base of a cellulose derivative and more particularly to a process for reclaiming dyed photographic film scrap which has a base of cellulose nitrate.

For many photographic purposes, photographic films are tinted or colored with a suitable dye which acts upon the film base or support to color it. The dye is usually applied to the film support upon the side opposite to which the light-sensitive silver halide emulsion is applied; the dye so applied does not normally penetrate more than a fraction of a thousandth of an inch. Various methods have been employed for removing this dye from the film base in order that the film base may be re-employed for various purposes, such as the manufacture of new film, lacquers, fabric coatings, etc. Under normal practice, the silver halide emulsion is removed from the film by the use of hot water following which the dye is bleached and/ or leached out of the film base.

Leaching with alcohol has been employed with success in some phases of film reclamation and bleaching of the film scrap is sometimes employed subsequent to the emulsion removal but prior to the leaching step.

It is among the objects of our invention to provide a simplified and efficient process of removing dye from photographic film scrap or the like which eliminates many of the steps and much of the cost and uncertainty of some of the prior known processes. It is a further object to remove the dye from film scrap by a hydrolyzing action. Other objects will appear hereinafter.

We have found that dyed cellulose nitrate film base may be reclaimed in a very simplified man her, after the silver halide emulsion has been removed by hot water treatment from the cellulose nitrate base by subjecting the film scrap to the action of an alcoholic solution of an alkali. Such treatment is neither a leaching nor a bleaching process but is a single step method by which the surface of the cellulose nitrate film base is hydrolyzed and actually removed from the film. By so timing the length of the treatment, or the concentration of the treating solution, the minimum amount of surface thickness may be hydrolyzed so as just to remove that portion of the surface into which the film dye has penetrated or the amount of alkali in the alcoholic solution thereof may be so limited that the alkali is just slightly in excess of that necessary to hydrolyze the film base to the same depth as that to which the dye has penetrated.

As an example of our process, we may subject lbs, of dyed cellulose nitrate film scrap from which the silver halide emulsion has been removed to the action of about 260 gallons of a solution of sodium hydroxide in denatured ethyl alcohol, the sodium hydroxide being present in amounts varying between about five hundredths of one per cent and five tenths of one per cent by weight or even more if desired, the solution being agitated. This treatment is carried on at approximately 120 F. and the duration of the treatment may b from 2 to 30 minutes, depending upon the color of the scrap being treated and the depth to which the color has penetrated into the film base. The treatment should be continued only to the point at which all of the color is removed, at which time the alcoholic solution should be quickly drained off from the film This treatment is followed by subsequent washings with warm alcohol and finally water to remove all traces of the treating solution and of the hydrolyzed portion of the base. Instead of using regular commercial alcohol as a solvent for the caustic soda, mixtures of this alcohol in water may be used, the water being present in amounts as high as about 40% by weight of the total solvent mixture. Also, instead of dissolving the sodium hydroxide directly in the alcohol, it is sometimes found expedient to first dissolve it in water to a concentrated solution and then to add sufficient of this concentrated solution to the alcohol or Water alcohol mixture to obtain the desired strength 01": sodium hydroxide.

Instead of forming the alcoholic solution of caustic soda by the addition of the caustic soda to the alcohol, the caustic soda may be created in situ by the slow addition to the alcohol with thorough stirring of a small amount of a substance which with the water contained in the alcohol will. form caustic alkali in solution. For instance, any of the compounds ammonium, sodium or potassium carbonate, tri-basic sodium phosphate or sodium peroxide may be utilized in this way with more or less success. Due to the small amount of water which is present in the alcohol employed, these substances react to form I the corresponding caustic alkali which goes into solution in the alcohol and accomplishes the same purpose as where the caustic itself is added to the alcohol, it being understood, of course,

that the film scrap is not usually placed in the alcohol before the alkali producing substance is added thereto. The other conditions necessary for carrying on the process are similar to those described above in connection with the use of alcohol to which the caustic has been added.

Merely because of the above specific examples, we do not intend to be limited in the spirit or scope of our invention, inasmuch as it will be apparent that various alcohols may be employed, so long as the alcohol is not a solvent of the film base and will dissolve the caustic added thereto and that other caustics may be employed, such, for instance, as potassium hydroxide etc, as is well known to those skilled in the art. All of these modifications and equivalents are, of course, to be considered within the scope of the claims appended hereto.

What we claim as our invention and desire to be secured by Letters Patent of the United States 1. The process of reclaiming dyed cellulose nitrate film scrap which comprises subjecting the film scrap base to the action of an alcoholic solution of an alkali.

2. The process of reclaiming dyed cellulose nitrate film scrap which comprises subjecting the film scrap base to the action of an alcoholic solution of a caustic alkali.

3. The process of reclaiming dye cellulose nitrate film scrap which comprises subjecting the film scrap base to the action of an alcoholic solution of sodium hydroxide. 4. The process of reclaiming dyed cellulose nitrate film scrap which comprises removing the silver halide emulsion from the film and hydrolyzing the surface of the film scrap base.

5. The process of reclaiming dyed cellulose nitrate film scrap which comprises removing the silver halide emulsion from the film and hydrolyzing the surface of the film scrap base with an alcoholic solution of an alkali.

6. The process of reclaiming dyed cellulose nitrate film scrap which comprises removing the silver halide emulsion from the film and hydrolyzing the surface or" the film scrap base with an alcoholic solution of a caustic alkali.

'7. The process of reclaiming dyed cellulose nitrate film scrap which comprises removing the silver halide emulsion from the film and hydrolyzing the surface of the film scrap base with an alcoholic solution of sodium hydroxide.

8. The process of reclaiming dyed cellulose nitrate film scrap which comprises removing the silver halide emulsion from the filin and hydrolyzing the surface of film scrap base to a depth approximately equal to that to which the dye has penetrated into the film base.

9. The process of reclaiming dyed cellulose nitrate film scrap which comprises hydrolyzing the surface or" the film scrap base with an alcoholic alkaline solution and then removing that portion of the film which has been hydrolyzed.

10. The process of reclaiming dyed cellulose nitrate film scrap which comprises hydrolyzing the surface of the film scrap base with an alcoholic alkaline solution to a depth approximately equal to that to which the dye has penetrated into the film base and then removing that portion of the film which has been hydrolyzed.

11. The process of reclaiming dyed cellulose nitrate film scrap which comprises hydrolyzing the surface of the film scrap base with alcohol containing a caustic alkali formed in situ and then removing that portion of the film which has been hydrolyzed.

12. The process of reclaiming dyed cellulose nitrate sheeting which comprises subjecting the sheeting to the action of an alcoholic solution of an alkali.

13. The process of reclaiming dyed cellulose nitrate sheeting which comprises subjecting the sheeting to ti e action of an alcoholic solution of a caustic alkali.

VALTER JOHN WEYERTS, KENNETH C. D. HICKMAN. 

